The Detroit Lions are bracing to be without Matt Stafford for four to six weeks atfer the quarterback suffered a shoulder injury in a season-opening loss to the Chicago Bears, according to a league source.

The QB was knocked out of the game on a blindside sack by Bears DE Julius Peppers just before halftime. He came out of the locker room in a sling during the second half.

While the Lions will not have Stafford undergo medical testing until Monday (an X-ray and possible MRI), they fear the former first-round pick will be out for at least four to six weeks, according to the source.

Stafford could end up being out longer as well, pending the results of those tests.